Stabilization of soap



Patented Apr. 12, 1949 STABILIZATION OF SOAP Elmer W. Cook, New York, N. Y., assignor to American Cyanamid Company, New York, N. Y., a corporation of Maine No Drawing. Application February 1, 1945,

Serial No. 575,733

3 Claims.

This invention relates to an improvement in soap and soap products, and more particularly to the incorporation into soap of a stabilizer having both antioxidant and a metal deactivating eflect,twhereby the soap is protected against discoloration and rancidity upon storage. By soap" -1 mean ordinary commercial soap, which is an alkali metal salt of a fat acid such as is obtained by the saponiflcation of vegetable or animal fats of the type of tallow, coconut oil and the like.

Most commercial grades of soap exhibit a tendency towards discoloration and rancidity upon storage. These undesirable changes are caused by oxygen of the air, the action of which is greatly accelerated by the presence of metal in the soap as an impurity, or by its storage in metal containers. My present invention is based on th discovery that a very eflective stabilization of the soap can be obtained by admixing therewith small quantities of stabilizers which contain, in chemical combination with each other, an antioxidant and a metal deactivating radical. It is known that biguanides and hydrocarbon substituted biguanides such as monoorthotolyl biguanide, mono-phenyl biguanide, mono-xylyl biguanide and bi-phenyl biguanide are antioxidants for soap; I have found that increased protection against discoloration and rancidity is obtained when these and similar biguanide antioxidants are combined with mercaptobenzothiazole to form a salt. Mercaptobenzothiazole possesses a specific deactivating effect on metal, and I have found that this metal-deactivating property is not diminished when the mercaptobenzothiazole is combined with biguanides to form salts. On the contrary, salts containing these two radicals in combination possess good anti- V stituted biguanide salts of mercaptobenzothiazole are new chemical compounds that have not previously been prepared. They are yellow, crystalline solids that are soluble in water and alcohol, and

lize. In practicing my invention the salts may be prepared separately and dissolved in aqueous soap, or the salt-forming ingredients may be incorporated with the soap during the dehydration thereof. In the latter case, the salt is formed and distributed uniformly throughout the soap as the latter is dried.

Although the invention in its broader aspects is not limited to the use of any particular biguanide, I prefer to use the mercaptobenzothiazole salts of the mono-aryl biguanides, and particularly the mono-phenyl and mono-tolyl biguanides, since these salts have produced excellent results in actual practice. Thus, for example, comparative large-scale tests were made in which commercial batches of soap, prepared in ordinary soap kettles and therefore containing traces of metallic impurities, were stored .for 6-month periods. One batch contained 0.1% of phenyl biguanide, based on the dry weight of the soap, while another batch contained an equal quantity of the mercaptobenzothiazol salt of phenyl biguanide. At the end of the test period it was found that the soap containing the mercaptobenzothiazole salt withstood storage considerably better than the soap which contained only the phenyl biguanide and was free from rancidity, light in color and of good appearance.

What I claim is: f

1. Soap stabilized against discoloration and rancidity by the presencetherein of stabilizing amounts of a biguanide salt of mercaptobenzothiazole, said soap being an alkali metal salt of a fat acid.

2. Soap stabilized against discoloration and rancidity by the presence therein of stabilizing amounts oi' a mono-phenyl biguanide salt of mercaptobenzothiazole, said soap being an alkali metal salt of a fat acid.

3. Soap stabilized against discoloration and rancidity by the presence therein of stabilizing Name Date 1,939,659 Calcott et al. Dec. 19, 1933 2,119,114 Richardson et al. May 31, 1988 2,123,928 Bousquet July 19, 1938 2,221,333 Sibley Nov. 12, 1940 2,397,960 Gribbins et al. Apr. 9, 1940 

